POS0332 CD71 RECEPTOR APICAL EXPRESSION IN ILEUM IS RELATED WITH HIGH LEVELS OF SERUM SIgA AND ACTIVITY DISEASE IN SpA PATIENTS
Authors: J. De Avila, A. Ramos-Casallas, D. Acero-M, C. Florez, V. Parra-Izquierdo, L. Chila, W. Bautista-Molano, A. Beltrán, D. Jaimes, J. M. Bello-Gualtero, C. F. Pacheco Tena, P. Chalem, C. Romero-Sánchez
Journal: Annals of the Rheumatic Diseases (2022)

Background Currently, mucosal immunity research has been investigated whether the serum levels of SIgA reflects the over-activation immune system in gut associated lymphoid tissues (GALT) and if the antigenic stimuli in the mucosa are responsible for inducing and maintaining the inflammatory response in Spondyloartrhitis (SpA). Based on our previous results, variances on levels of SIgA might influence in disease activity. SIgA Reverse transcytosis (retrotranscytosis) has been demonstrated as a GALT mechanism which enhance systemic inflammation in some autoimmune pathologies such as celiac disease. Objectives This study proposes the evaluation of receptors associated with retrotranscytosis CD71 and Dectin-1 (Dec-1) in gut tissues from SpA without IBD patients to explore a possible mechanism responsible of gastrointestinal inflammatory imbalance. Methods In total, 180 patients with SpA (ASAS/criteria) were assessed by rheumatologists, of which (n=65, 36.1%) met the selection criteria and from them (n=41, 63.1%) by a gastroenterologist to perform digital chromoendoscopy with magnification for colon e ileum and histological analysis. Pregnant and lactating women, and cancer patients, patients with other autoinflammatory diseases, autoimmune diseases, immunodeficiency, chronic pancreatitis, or chronic liver disease, and those who had received antibiotic treatment in the last 3 months were excluded from the study. Furthermore, those patients with SpA and concomitant IBD were excluded. All included patients were between 18 and 65 years old. CD71 and Dec-1 apical expression were identified by indirect immunofluorescence. Fecal Calprotectin (FC), Serum SIgA in house and clinical indices BASDAI, BASFI, ASDAS-CRP, ASDAS-ESR were measured. The association were evaluated using the Chi-square or Fisher’s exact test and a multiple correspondence discriminant analysis (MCDA) was performed including those variables with significant associations from bivariate analysis and some that are considered clinically relevant to explain the impact of SIgA and CD71 in SpA. Results The average age of the patients included was 44,6±10.2 years, 56.1% were men, 39.0% were HLA-B*27:05 positive, 90.2% had axial involvement. Serum levels of SIgA were 62.3±24.1 gr/mL, CRP 1.7±2.4 and ESR 14.1±12.0 mm/h. Positive levels of FC (&gt;120ng/mL) were observed in 31.7%. BASDAI &gt;4 was found in 58.5% of patients and ASDAS-CRP &gt;2.1 in 75.6%. Apical expression of CD71 and Dec-1 in the ileum was observed in 48.8% and 36% respectively, the expression of both receptors in colon tissues were irrelevant. CD71 expression was associated with high levels of serum SIgA (p=0.05). However, no associations were observed between retrotranscytosis receptors and any of the clinical and histological variables. The MCDA showed a Cronbach’s Alpha reliability coefficient of 0.763 and showed two dimensions: a main dimension (Dim 1) related to the presence of loss of the vascular pattern in the ileum (CC 0.325), FC + diarrhea (CC 0.695), FC + abdominal distension (CC 0.883) and FC + abdominal pain (CC 0.885) and a secondary dimension (Dim 2) that collected the variables serum SIgA (CC 0.513), ASDAS-CRP &gt;2.1 (CC 0.311), CD71 (CC 0.424), please see Figure 1. Figure 1. Multiple correspondence discriminant analysis for CD71, serum SIgA and activity index in SpA patient Conclusion The findings reflect a possible relationship among the apical expression of CD71in ileum with high levels of serum SIgA and activity, suggesting that retrotranscytosis mediated by this receptor might be a mechanism that mediate the intestine-joint axis in SpA. Acknowledgements The Ministry of Science, Technology, and Innovation - MinCiencias (Grants No. 68022 and 57442). Universidad El Bosque (PCI-2018-10300), Hospital Militar Central (Grant 2017-023), Clínicos IPS, Gastroadvanced, Fundación Instituto de Reumatología Fernando Chalem, in Bogota, Colombia and Biomedicina de Chihuahua, México Disclosure of Interests None declared